Since guest threads get exactly the stack size they request, host code
that a guest thread calls runs on that small stack too. sceAgcCreateShader
reaches Driver::RegisterShader, whose frame alone is about 50 KiB, so a
title whose job threads ask for 48 KiB overflows the stack (#2603).
Each guest thread now gets a fixed 1 MiB of host stack below the range it
asked for. The guest still sees the requested size and address range
through scePthreadAttrGet and sceKernelIsStack; only host calls made from
the thread use the extra room. Running the prepared-shader driver tests on
a limited main-thread stack needs between 128 and 192 KiB for shader
registration, Vulkan setup included, so 1 MiB leaves several times that.
Switching to a separate host stack at each HLE entry point would need a
trampoline on every export that may go deep, handling of stack-passed
arguments and unwinding across the switch, and a list of which exports
qualify. A margin below the guest range covers every host call with no
per-export list.
On Windows the committed size was the requested size, and the margin
below it depended on the executable's default stack reserve; requests at
or above that reserve had none. The commit now includes the same margin.
macOS does not run guest threads.
guest_pthread_stack now also calls host code that uses 256 KiB of stack
below each thread's guest range; without the margin it crashes on the
16 KiB thread.
Fixes#2603
84d90152b4